The PbFRK1 gene from pear fruit affects sugar accumulation

Soluble sugar is an important component of pear fruit quality. As a key enzyme of hexose metabolism, hexokinase is closely related to pear fruit quality. However, there are few research reports on the fructokinase (FRK) gene family, consisting of hexose phosphorylases, in pear. Therefore, in this study, two pear varieties, 'Yali' and 'Aikansui', were used as test materials to study the effects of bagging, a widely used cultivation technique in pear fruit production, on the soluble sugar content and hexokinase activity of pear fruit during the growth process; analyze the response of hexokinase to bagging treatment and the correlation between hexokinase activity and soluble sugar content; and clone the fructokinase gene PbFRK1 from pear fruit. The results showed that bagging treatment inhibited the accumulation of sugar in the fruit to a certain extent. PbFRK1 gene expression was positively correlated with hexokinase activity but negatively correlated with the content of soluble sugar components. In addition, we overexpressed PbFRK1 in tomato. The results showed that the growth of transgenic tomato plants was inhibited, and the soluble sugar content of transgenic tomato plants was significantly lower than that of the wild-type control, while the activity of hexokinase was higher than that of the wild-type control. Therefore, in pears, PbFRK1 seems to be involved in regulating the activity of hexokinase, thereby regulating the sugar content of fruits and affecting plant growth and development. This study is not only meaningful for understanding the molecular mechanism of fruit sugar metabolism but also helpful for guiding breeding and production.